This invention relates to pneumatic tires for vehicles and more particularly to such tires having a runflat capability and to the hubs adapted for use with such tires.
Presently known automobile tires are generally quite reliable. When, however, they do fail, they become a source of substantial difficulty. Thus, when air is lost from a tire, due either to a puncture of the tire by a foreign body or to a blow-out of the tire, both of which result in the tire becoming "flat", it becomes necessary to change the tire for a "spare" which is customarily carried in the vehicle. The changing of a tire can be a dangerous operation. For example, if it is necessary to change a tire while the vehicle is on a roadway, the person changing the tire is exposed to, and runs a substantial risk of being struck by, other vehicles on the road. Furthermore, after jacking up the vehicle so that the tire may be changed, it is possible for the jack to slip or for the vehicle itself to roll, thereby causing physical injury to the tire changer. If on the other hand the driver of the vehicle does not wish to expose himself or his passengers to the possibility of such injury, the driver may attempt to drive onward while the flat tire remains on the vehicle until he reaches a safe place to change the tire or until he reches an auto service station where the tire will be repaired and replaced for him. This however, frequently results in the complete destruction of the tire, and possibly of the hub on which the tire is mounted as well. The destruction of the tire may be caused by the heat resulting from the chafing of the inner portions of the tire against one another, the coefficient of friction of dry rubber being quite high. The heat generated in this manner causes rapid tire cord deterioration and thus rapid tire destruction. The destruction of the tire may also be caused by the slippage of the tire on the hub which allows the flanges or rims of the metal hub to be ground into the tire, thereby tearing and cutting the tire. The metal hub may be damaged beyond repair by being deformed under the weight of the vehicle as the hub rolls along the surface of the road, the shock absorbing capacity of the air filled tire no longer being available to protect the hub.
In an attempt to overcome the above-noted difficulties, tires having an annular lining constituted by an elastomeric material positioned in the central portion of the hub have been provided. The purpose of the lining is two-fold, one reason being to clamp the beads of the tire between the lining and the rims or the flanges of the hub, thereby preventing the detachment of the tire from the hub following tire failure, and the second reason being to provide support for the radially inner central tread portion of the tire, thereby causing the tire to be relatively stable. This solution, however, is not completely satisfactory because the stability of the tire is dependent upon driving the vehicle at a slow speed and then only for a short distance. If an operator attempts to drive at a moderate rate of speed, or at a slow speed but over an extended distance, it has been found that the tire will oscillate perpendicularly to the direction of vehicle travel, resulting in the separation of the tire from the hub or otherwise causing the destruction of the tire.